From the Manufacturer

The W8S is a trapezoid sub-bass enclosure designed for use with the W8 full-range system in situations where low-frequency enhancement and extra headroom are required. Its unique hybrid horn/reflex design combines the benefits of the fast transient bass performance of a folded horn with the extreme low-frequency extension of a reflex enclosure. The horn and reflex sections are entirely separate – the folded horn section being powered by a high efficiency 15″ (380mm) driver and the reflex section powered by a high power 18″ (460mm) device. Both drivers utilise high temperature 4″ (100mm) voice coils. This combination of horn and reflex technology within a single enclosure results in a dynamic sub-bass with an efficiency of 104dB, with acoustic addition of the separate sections being maintained up to 150Hz. The physical dimensions of the W8S are identical to the W8. It is constructed from multi-laminate birch ply and is fully equipped for touring with rear castors, grille protection and handles. It is fitted with load certified MAN flying points identical to those in the W8, allowing it to be flown with the W8 as part of the main Wavefront array. For many applications, it may be preferable to ground stack the W8S sub-bass enclosures some distance away from the main Wavefront array. Because the low-mid of the flown W8 can operate down to 80Hz, there is no loss of acoustic power in the 100-150Hz region when the W8S sub-bass is ground stacked in this way